The grieving families of the 28 people who were killed in a coach crash in
Switzerland are visiting the site of the tragedy today.

The visits, which have been arranged for the families throughout the day, come as it emerged the driver of the coach may have suffered a heart-attack at the wheel which caused the accident on Tuesday night.

"The visits are going on at the moment. They have been organised for the whole day on the request of the families," a police spokesman told AFP.

Twenty-two children and six adults were killed in the tragedy.

Investigators said they had ruled out speeding and believed the accident, which occurred in clear conditions on a relatively quiet road, may have been the result of ill health or driver error.

The crash, in which 28 people were also seriously injured, happened shortly after the party of 52 schoolchildren and staff from Belgium and Holland set off for home following a holiday in the Alpine ski resort of Val d’Annivers.

The coach entered the westbound Sierre tunnel on the A9 motorway at around 9.15pm on Tuesday and clipped the kerb in the outside lane. It lurched across the carriageway and careered into a concrete wall at the end of a hard shoulder.

(SEBASTIEN FEVAL/AFP/Getty Images)

Most of the children are believed to have been wearing seatbelts, but investigators said such was the force of the impact that it did little to prevent the catastrophic loss of life.

Olivier Elsig, a Swiss prosecutor in charge of the investigation, said there were no indications that the crash had been caused by excessive speed.

There were two drivers on board. They had arrived in Switzerland the day before and had rested fully before setting off on the journey. Both were killed in the accident.

Mr Elsig told a press conference in the Swiss town of Sion that the possibility that the driver had died at the wheel was one theory being examined.

He said a number of witnesses were being questioned, including other motorists, and that a post mortem examination was being conducted on the driver.

Flowers placed on the bridge overlooking the site where the coach crashed near Sierre (AFP/Getty Images)

Elio Di Rupo, the Belgian prime minister, described the accident as a “black day for our country”.

The victims came from St Lambert School, in the north eastern Belgian town of Heverlee, and from the Stekske School in Lommel, on the Belgian border close to the Dutch city of Eindhoven. Among the 28 dead were seven children from Holland. A German and a Polish national were also among the injured.

One 12-year-old girl who survived the crash described hearing a huge bang before being thrown violently forward.

Belgium’s Le Soir newspaper said the girl, who suffered two broken legs and a broken arm, had told her father by phone: “It was dark. I heard a great bang. All the seats were gone. I found myself wedged between two seats.”

One of the teachers on board the coach, Frank Van Kerckhove, was confirmed as one of the six adults killed. The bodies of the dead were taken to a funeral home in the town of Sion.

Because of the extent of the injuries suffered by those on board, the Swiss and Belgian authorities were unable to provide full details of which children had died.

Parents of the victims, who met Mr Di Rupo and the King of Belgium, were flown on a military aircraft to Switzerland, many of them not knowing if their children were alive or dead.

A female motorist, who was the first person on the scene, described the horror of dead and dying children. The mother of two, who was named only as Marielle, had been driving just moments behind the coach when it smashed into the tunnel wall.

“I saw the front seats of the bus all smashed against each other and there was blood everywhere and I saw children who were still alive waving to be saved,” she said. “It was horrific. I imagine the pain of the parents. If this had been my children I don’t know what I would do. I can still see all those faces staring at me. I don’t even know if they were alive or dead. It was horrible.”

Claude Peter, head of the Val d’Annivers rescue service, said he was shocked by the scenes when he arrived at the crash site. “You could not even hear children’s cries. In these situations the children are mute; they are in so much shock. Above all, it was the injuries that were most graphic. I have a 12-year-old son and to see all these injured children of the same age was really shocking.”

The party, which had arrived in Switzerland on March 3 for a nine-day trip, had charted their adventures on a daily blog, packed with smiling photographs and messages to their parents telling them how much fun they were having.

At around 8.30pm on Wednesday, three coaches had set off from the resort of Saint-Luc for the long journey back to Belgium.

Two of the coaches passed through the Sierre tunnel safely but the third crashed just after 9.15pm.

The wife of one of the dead drivers, Evy Laerman, described how she had feared the worst when her husband failed to contact her at a pre-arranged time.

“I tried to phone him but the call went straight to his voicemail,” she said. “I then went on to the internet and learned about the crash and read that both drivers were killed.”

“I am trying to be strong but in fact I just feel numb. It just hasn’t sunk in and I’m functioning on autopilot.”

Melchior Wathelet, the Belgian transport secretary, confirmed that the coach, which was registered in 2002, belonged to the Toptours, a company based in the town of Aarschot.

He said the company had an excellent reputation and a good safety record.

Toptours, which runs a fleet of 14 coaches, specialises in winter sports, and regularly transports passengers from Belgium to Austrian and Italian resorts.

Jan Luykx, the Belgian ambassador to Switzerland, said: “This tragedy will devastate the whole of Belgium. All of the victims came from two villages.

“The scale of the accident is impossible to digest. We are currently focusing on the practical aspects of dealing with this tragedy.”